Indigo, sometimes called indigo dye, is probably the oldest dye or pigment used by humans. It was originally obtained from plants in the Indigofera and Isatisgenera. In 1878, A. von Baeyer synthesized it from isatin; 12 years later, K. Heumann developed a commercial process; and by the end of the 19th century, most indigo dye was synthetic. Indigo is insoluble in water, so dyers treat yarn with alkaline solutions of the yellow reduced form leucoindigo, which oxidizes to indigo when the yarn is exposed to air.
January 22, 2018
Indigo is the oldest dye or pigment used by humans; and the manufactured product is still in use today. Recently, John E. Dauber at the University of California, Berkely, developed a biochemical process to make indigo that is not only environmentally “green”, but it also allows cotton fabric to be treated with an indigo precursor, which then oxidizes in place to dye the fabric.
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